[Cialug] How is this possible?

[Tom Sellers]

I have a small desktop computer with two wired network connections.  One is
built into the motherboard and the other is a 3com network card that I have
added.

The built in network card should be eth0 and the added card should be
eth1.  The eth0 wired connection is set to use dhcp while the eth1 wired
network card is assigned an IP.

When I boot the system up with no network cable connected to eth0 and a
cable to my dhcp network on eth1and run ifconfig. I get a display that
indicates eth0 has an IP on my dhcp network and eth1 shows the assigned ip
given it.

 When I ping the dhcp network address I get a response and when I ping the
assigned IP I also get a response.  Both appear to be using the added
network card (eth1) even though the two network connections show separate
hardware addresses.

Can anyone explain how this is possible?

This all started when I was unable to get linux to get a dhcp address on
eth0 with both network jacks cabled to their respective networks.  I didn't
think the same card could have two separate IP addresses.

Not that familiar with linux!